Detecting and using GHC_PACKAGE_PATH would allow "stack exec" support. This way propellor would be able to be built with

stack build

and run with

stack exec -- propellor ...

see https://github.com/yesodweb/yesod/issues/1018 and https://github.com/yesodweb/yesod/commit/a7cccf2a7c5df8b26da9ea4fdcb6bac5ab3a3b75

I don't think stack exec propellor makes sense to use. Instead, stack install propellor and then put that in PATH. I've now made propellor --init know when it was built using stack, and it will set up propellor to continue to build itself using stack. done --Joey